560 



MOLLUSCA 



PHYLÜM VI 



columellar border sliglitly twisted, witli two or tliree small oblique plaits anteriorly ; 

 sometimes umbilicate. Cretaceous to Receiit. 



Pisanella v. Koenen. Oligocene. Peristernia Möreli ; Leucozonia Gray. Tertiary 

 and Eecent. 



Family 6. Vasidae Adams. {Turhinellidae auct.). 



Shell similar to those of the preceding family, but with strong, horizontal columellar 

 folds. Tertiary and Recent. 



Xancus Bolt. {Tmhinella Lam. ; Mazza Adams ; Mazzalina Conrad). Tliick- 

 shelled, ovate - conical, smooth ; spire sliort and blunt, body wliorl large ; canal 

 straiglit, elongated. Eocene to Recent. 



Vasum Link {Gynodonta Schum.). Shell lieavy, strongly scnlptured, often spinöse, 

 witli short canal. Tertiary and Recent, 



Family 7. Volutidae Gray. 



Shell thicJc, ovate to fusiform, dull or lustrous. Spire short or long, hody whorl large. 

 Aperture elongated, with a short canal or notch ; inner lip with columellar folds. Oper- 

 culum usually ahsent Cretaceous to Recent. 



This family, as liere defined, contains genera distributed by malacologists amongst 



several families — Marginellidae, Mitridae and 

 Volutidae — all of whicli are cliaracterised by tlie 

 strong development of columellar folds; but it is 

 likely tliat this structure originated independently 

 in several phyla at intervals remote from one 

 another. The Initiation of well-marked genera 

 with Volutoid plaits occurred in the Cretaceous. 

 Subsequently their number increased, and a great 

 many generic types became dift'erentiated. The 

 phylogeny of Tertiary and Recent forms has been 

 ably worked out by DalL^ 



Marginella Lam. (Fig. 1031). Shell oval or 

 oblong, smooth, glistening. Spire short ; aperture 

 narrow, slightly canaliculate anteriorly.' Columella 

 with three or four oblique folds of about equal 

 size ; outer margin frequently thickened and dentate. 

 Tertiary and Recent. 



Mitra Lam. (Fig. 1032), Fusiform to elongate- 

 oval, solid ; spire high, acuminate ; aperture narrow, 

 channelled anteriorly. Columella with numerous 

 oblique folds, the posterior plaits 



being often the strongest. Outer margin commonly thickened, and 



smooth internally. Abundant in the Tertiary and Recent. 



Turricula Adams. Like the last, but shell transversely ribbed. 



Cretaceous to Recent, 



Strigatella Swains. (Fig. 1033) ; Gylindromitra Fischer {Cylindra 



Schum.) ; Imhricaria Schum, ; Volutomitra Gray ; Perplicaria Dali, 



Tertiary and Recent, 



Lyria Gray (Fig, 1034). Elongate - oval, transversely ribbed. 



Aperture narrow. Columella anteriorly with two much compressed 



Fig. 1031. 



Marginella crassula 

 Desh. Calcaire Gros- 

 sier; Chaumont, near 

 Paris. 2/j. 



Fig. 1032. 



Mitra fusiforniis 

 Brocchi. Plio- 



cene ; Rhodes. 



1 Bull. Museum Comp. Zoology, vol. xviii., 1889 ; Proc. U.S. Nat. 

 Museum, vol. xii., 1890, Trans. Wagner Free lust. Sei. Pliilad., vol. iii,, 1890. 



Strigatella lahratula 

 (Lam.). Eocene; 

 Grignon, near Paris, 



